(1) Field of the Invention
This invention relates to photopolymerizable compositions, and to methods of producing positive and negative polymeric images from these compositions.
(2) Description of the Prior Art
Conventional polymeric imaging systems are of the negative polymeric image type; that is, the photopolymerizable coating is exposed to radiation through a process transparency and a negative polymeric image is produced. By "negative polymeric image" is meant a polymeric image which corresponds to the transparent portions of the process transparency.
Recently systems which provide a positive polymeric image have been developed. One such system is described by Nebe in U.S. Pat. No. 4,029,505. In this system
(a) a substrate is coated with a photopolymerizable composition containing PA0 (b) the photopolymerizable coating is exposed through a process transparency to radiation at least some of which has a wavelength less than 3400 A whereby the nitroso dimer is dissociated to a polymerization-inhibiting nitroso monomer in the radiation-struck areas, and PA0 (c) a greater portion of the photopolymerizable coating is exposed to radiation substantially limited to wavelengths greater than 3400 A whereby a positive polymeric image is formed in the areas struck by the second radiation but not struck by the first imagewise radiation.
(1) a nongaseous, ethylenically unsaturated, polymerizable compound, PA1 (2) 0.001 to 1.0 part by weight per part of polymerizable compound of an organic, radiation-sensitive, free-radical generating system, and PA1 (3) 0.1 to 10% by weight, based on the photopolymerizable composition, of a nitroso dimer PA1 (1) an ethylenically unsaturated monomer, PA1 (2) a photopolymerization initiator system comprising a photo-oxidant dye and a reducing agent for the dye, and PA1 (3) an ionizable desensitizing agent having a nitrobenzyl moiety in combination with a carboxylate group, PA1 (a) a normally nongaseous, ethylenically unsaturated compound capable of addition polymerization by free-radical initiated chain propagation, PA1 (b) about 0.004 to about 0.7 part by weight, per part of component (a), of nitroaromatic compound of the formula ##STR1## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4, alike or different, are H, OH, halogen, NO.sub.2, CN, alkyl of 1 to 18 carbons, alkoxy in which the alkyl is of 1 to 18 carbons, acyloxy of 2 to 7 carbons, aryl of 6 to 18 carbons, benzyl, halogen-substituted phenyl, polyether of 2 to 18 carbons and 2 to 10 oxygens, dialkylamino in which each alkyl is of 1 to 18 carbons, thioalkyl in which the alkyl is of 1 to 18 carbons, or thioaryl in which the aryl is of 6 to 18 carbons, R.sup.2 and R.sup.3, taken together, are --OCH.sub.2 O-- or --O--CH.sub.2 CH.sub.2 O).sub.q in which q is an integer from 1 to 5, or any two of R.sup.1, R.sup.2, R.sup.3 and R.sup.4, taken together, are the residue of a second benzene ring fused into the benzene nucleus, with the proviso that not more than one of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is OH or NO.sub.2, PA1 (c) about 0.001 to about 10 parts by weight, per part of component (a), of an organic, radiation-sensitive, free-radical generating system, activatable by actinic radiation that does not significantly rearrange the nitroaromatic compound to an inhibitor of free-radical polymerization. PA1 (1) coating the substrate with the above photopolymerizable composition, PA1 (2) imagewise exposing a portion of the photopolymerizable coating through an image-bearing transparency to radiation at least about 20% of which has a wavelength of about 200 to about 380 nm, thereby rearranging at least some of the nitroaromatic compound to polymerization-inhibiting nitrosoaromatic compound, and PA1 (3) subjecting the coating to a second exposure whereby a greater portion of the coating, including the portion exposed during the imagewise exposure, is exposed to radiation substantially limited to wavelengths greater than about 380 nm, whereby a positive polymeric image is formed in the areas exposed during the second exposure, but not exposed during the imagewise exposure. The image formed in step (3) is developed by removing the nonpolymerized portion of the photopolymerizable coating in the areas exposed to the imagewise exposure radiation, or by differential adhesion of a pigment toner to the unpolymerized portion of the photopolymerizable coating in the areas exposed to the imagewise exposure radiation. PA1 (1) coating the substrate with the above photopolymerizable composition, and PA1 (2) imagewise exposing a portion of the photopolymerizable coating through an image-bearing transparency to radiation substantially limited to wavelengths greater than about 380 nm, whereby a negative polymeric image is formed in the areas exposed to to the radiation. PA1 N-phenyl-N-methylacrylamide, PA1 N-vinylphthalimide, PA1 diacetone acrylamide, PA1 N-vinylsuccinimide, PA1 p-xylylene diacrylate, PA1 1,4-bis(2-acryloxyethyl)benzene, PA1 pentaerythritol triacrylate, PA1 4-acryloxybenzophenone, PA1 4-methacryloxybenzophenone, PA1 N-(2-acryloxyethyl)succinimide, PA1 1,1,1-trimethylolpropane triacrylate, PA1 pentaerythritol tetraacrylate, PA1 triethylene glycol diacrylate, PA1 triethylene glycol dimethacrylate, PA1 1,1,1-trimethylolpropane trimethacrylate, PA1 4-acryloxydiphenylmethane, PA1 N-(2-acryloxypropyl)succinimide, PA1 2,4-diacryloxybenzophenone, PA1 4-(.alpha.,.alpha.-dimethylbenzyl)phenyl acrylate, PA1 3-acryloxybenzophenone, PA1 2-acryloxybenzophenone, PA1 2-acryloxy-4-octyloxybenzophenone, and mixtures thereof. The most preferred polymerizable compounds are esters of .alpha.-methylenecarboxylic acids selected from the group consisting of acrylic and methacrylic acids. PA1 R.sup.1 is H or methoxy; PA1 R.sup.2 and R.sup.3 are H, alkoxy of 1 to 6 carbons, polyether of 2 to 18 carbons and 2 to 10 oxygens, alkyl of 1 to 6 carbons, or acetoxy; or PA1 R.sup.2 and R.sup.3, taken together, are --OCH.sub.2 O-- or --O--CH.sub.2 CH.sub.2 O).sub.5 ; PA1 R.sup.4 is H; PA1 R.sup.5 is H, alkyl of 1 to 6 carbons, alkoxy of 1 to 6 carbons, or phenyl; PA1 R.sup.6 is OH, alkoxy of 1 to 6 carbons, or phenoxy substituted with up to three chlorines, alkyls of 1 to 6 carbons, or alkoxys of 1 to 6 carbons; or PA1 R.sup.5 and R.sup.6, taken together, are .dbd.O, .dbd.NC.sub.6 H.sub.5, .dbd.N(hydrocarbylene) ##STR6## in which the hydrocarbylene group is of 2 to 6 carbons, .dbd.N (alkyl) in which alkyl is n-alkyl of 1 to 6 carbons or t-butyl, or ##STR7## in which R.sup.8 and R.sup.9 are alike and are H or methyl, and R.sup.7 and R.sup.10 are alike and are --CN, --COR.sup.11 in which R.sup.11 is methyl or ethyl, or --COOR.sup.12 in which R.sup.12 is methyl or ethyl. PA1 R.sup.1 and R.sup.4 are H; PA1 R.sup.2 and R.sup.3 are alike and are alkoxy of 1 to 6 carbons; PA1 R.sup.5 is H, or alkyl of 1 to 6 carbons; PA1 R.sup.6 is alkoxy of 1 to 6 carbons, or phenoxy substituted with up to two alkoxys of 1 to 6 carbons; or R.sup.5 and R.sup.6, taken together, are .dbd.O or .dbd.NC.sub.6 H.sub.5. PA1 o-nitrobenzyl alcohol, PA1 o-nitrobenzaldehyde, PA1 .alpha.-phenyl-o-nitrobenzyl alcohol, PA1 o-(diphenylmethyl)nitrobenzene, PA1 .alpha.-phenylimino-o-nitrotoluene, PA1 .alpha.,.alpha.-diethoxy-o-nitrotoluene, PA1 .alpha.,.alpha.-ethylenedioxy-o-nitrotoluene, PA1 3-methoxy-2-nitrobenzaldehyde, PA1 4-methoxy-2-nitrobenzaldehyde, PA1 3,4-dimethoxy-2-nitrobenzaldehyde, PA1 3,4-dimethoxy-2-nitrobenzyl alcohol, PA1 4-cyano-2-nitrobenzaldehyde, PA1 5-hydroxy-2-nitrobenzaldehyde, PA1 4-hydroxy-3-methoxy-2-nitrobenzaldehyde, PA1 1-nitro-2-naphthaldehyde, PA1 2,3,4,5-tetramethyl-6-nitrobenzyl alcohol, PA1 3,4,5-trichloro-2-nitrobenzaldehyde, PA1 3,5-dibromo-4,6-dichloro-2-nitrobenzaldehyde, PA1 4,5-dimethoxy-2-nitrobenzyl alcohol, PA1 4,5-dimethoxy-2-nitrobenzaldehyde, PA1 2,4-dinitrobenzaldehyde, PA1 5-tolyl-2-nitrobenzaldehyde, PA1 5-benzyl-2-nitrobenzaldehyde, PA1 5-(m-chlorophenyl)-2-nitrobenzaldehyde, PA1 4-(2-methoxyethoxy)-2-nitrobenzaldehyde, PA1 4-ethoxyethyl-2-nitrobenzaldehyde, PA1 3-diethylamino-2-nitrobenzaldehyde, PA1 4-butylthio-2-nitrobenzaldehyde, PA1 4-phenylthio-2-nitrobenzaldehyde, PA1 2-nitrostyrene, PA1 4,5-dimethoxy-2-nitrostyrene, PA1 .alpha.-(p-dimethylaminophenyl)imino-2-nitrotoluene, PA1 4,5-dimethoxy-2-nitro-.alpha.-phenyliminotoluene, PA1 2-nitrostyrene oxide, PA1 2-nitrocumene, PA1 4,5-dimethoxy-2-nitrobenzyl chloride, PA1 .alpha.,.alpha.-ethylenedioxy-2-nitrotoluene, PA1 N,N'-bis(4,5-dimethoxy-2-nitrophenylmethylene)-1,6-hexanediamine, PA1 N,N'-bis(2,4-dinitrophenylmethylene)-2,5-dimethyl-2,5-hexanediamine, PA1 N,N'-bis(4,5-dimethoxy-2-nitrophenylmethylene)-m-phenylenediamine, PA1 N,N'-bis(4,5-dimethoxy-2-nitrophenylmethylene)-p-phenylenediamine PA1 N,N'-bis(4,5-dimethoxy-2-nitrophenylmethylene)-.alpha.,.alpha.'-bi-p-toluid ine, PA1 N,N'-bis(4,5-dimethoxy-2-nitrophenylmethylene)-4,4'-stilbenediamine, PA1 dimethyl ester of 2,6-dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid, PA1 diethyl ester of 2,6-dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid, PA1 diethyl ester of 2,6-dimethyl-4-(2'-nitro-4',5'-dimethoxyphenyl)-1,4-dihydropyridine-3,5-di carboxylic acid, PA1 di-n-propyl ester of 2,6-dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid, PA1 diisopropyl ester of 2,6-dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid, PA1 di(.beta.-ethoxyethyl)ester of 2,6-dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid, PA1 diallyl ester of 2,6-dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid, PA1 dipropargyl ester of 2,6-dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid, PA1 3-methyl-5-ethyl ester of 2,6-dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid, PA1 3-isopropyl-5-methyl ester of 2,6-dimethyl-4-(2'-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid, PA1 ethyl ester of 4-(2'-nitrophenyl)-2,6-dimethyl-3-aceto-1,4-dihydropyridine-5-carboxylic acid, PA1 2,6-dimethyl-4-(2'-nitrophenyl)-3,5-diaceto-1,4-dihydropyridine, PA1 2,6-dimethyl-4-(2'-nitrophenyl)-3,5-dicyano-1,4-dihydropyridine, PA1 ethyl ester of 2-methyl-4-(2'-nitrophenyl)-1,4,5-6,7,8-hexahydro-5-oxoquinoline-3-carboxy lic acid, PA1 methyl ester of 2-methyl-4-(2'-nitrophenyl)-1,4,5,6,7,8-hexahydro-5-oxoquinoline-3-carboxy lic acid, PA1 isopropyl ester of 2-methyl-4-(2'-nitrophenyl)-1,4,5,5,6,8-hexahydro-5-oxoquinoline-3-carboxy lic acid, PA1 1,2,3,4,5,6,7,8,9,10-decahydro-9-(2'-nitrophenyl)-1,8-dioxoacridine, PA1 1,2,3,4,5,6,7,8,9,10-decahydro-3,3,6,6-tetramethyl-9-(2'-nitrophenyl)-1,8-d ioxoacridine, PA1 1-(2'-nitro-4',5'-dimethoxy)phenyl-1-(4-methoxyphenoxy)ethane, PA1 1-(2'-nitro-4',5'-dimethoxy)phenyl-1-phenoxyethane, PA1 1-(2'-nitro-4',5'-dimethoxy)phenyl-1-(2,4-dimethylphenoxy)ethane, PA1 1-(2'-nitro-4',5'-dimethoxy)phenyl-1-(4-chlorophenoxy)ethane, PA1 1-(2'-nitro-4',5'-dimethoxy)phenyl-1-(4-bromophenoxy)ethane, PA1 1-(2'-nitro-4',5'-dimethoxy)phenyl-1-(2-naphthyloxy)ethane, PA1 1-(2'-nitro-4',5'-dimethoxy)phenyl-1-(2,4-dimethoxyphenoxy)ethane, PA1 1-(2'-nitro-4',5'-dimethoxy)phenyl-1-(4-t-butylphenoxy)ethane, PA1 1-(2'-nitro-4',5'-dimethoxy)phenyl-1-(2-t-butylphenoxy)ethane, PA1 2-nitro-4,5-dimethoxy-.alpha.-methyliminotoluene, PA1 2-nitro-4,5-dimethoxy-.alpha.-t-butyliminotoluene, PA1 2-nitro-4,5-dimethoxy-.alpha.-n-butyliminotoluene, PA1 2-nitro-4,5-dimethoxy-.alpha.-n-hexyliminotoluene, and PA1 1-(2'-nitro-4',5'-dimethoxy)phenyl-1-(2,4,5-trimethylphenoxy)ethane.
Although this system can produce excellent positive polymeric images, a limited time factor is involved. The second exposure must be carried out soon after the first exposure since the nitroso monomer formed during the first exposure can recombine to form inactive nitroso dimer. It would also be desirable to have a system which is not dependent on exposure to such short wavelength radiation.
Another system for producing positive polymeric images is described by Margerum in U.S. Pat. No. 3,556,794. In this system, a photopolymerizable material comprising
is imagewise exposed to radiation in the wavelength range of 2000-4000 A, thereby inhibiting polymerization by the desensitization of the initiator system, and exposing the photopolymerizable material to radiation in the wavelength range of 3800 to 7200 A, thereby producing a polymeric image in the area not exposed to the imagewise radiation. This system suffers from the drawback that the desensitizing effect of the desensitizing agent is only temporary. Margerum states that the desensitization lasts "for up to about fifteen or more minutes". In Example 1 the second exposure follows the imagewise exposure by 30 seconds.